The present invention relates to mixing solid pieces with a liquid, and more particularly, but not exclusively, relates to coating and coloration of landscaping materials.
The problem of landfill crowding has grown steadily. One way to reduce this crowding is to recycle as many materials as possible. One type of material suitable for recycling is wood. Wood may arrive at the landfill from a natural source, such as discarded tree branches, or it may be derived from various discarded products, such as shipping crates and furniture.
One way to recycle wood is to reduce the wood to a number of pieces of generally uniform size with a shredder, chipper, or grinder. Such comminuted wood is often suitable for use as a landscaping mulch. However, the varied types of wood typically obtained from a landfill often result in a non-uniform coloration that significantly changes with age and exposure to the elements. To alleviate this problem, recycled wood pieces are sometimes treated with a colorant to provided a more pleasing appearance. U.S. Pat. No. 5,308,653 to Rondy describes one coloring process.
One problem often encountered with coloring processes is excessive run-off of liquid colorants used to impart a uniform appearance to the wood pieces. This run-off adversely impacts cost effectiveness. To address this problem, there is a need to optimize the coloration process by determining the minimum amount of liquid colorant needed for a given amount of wood. There also remains a need to provide a more cost effective way to uniformly color landscaping material.
Another problem with the coloration process is that mixers used to blend liquid colorant and wood pieces are subject to frequent jamming. Typically, the mixer becomes packed with a mass of wood chips that are stuck together. This mass of chips often prevents discharge of the treated product from the mixer. Equipment down time to unclog the mixer generally increases processing costs and may result in excessive colorant run-off. Thus, there is also a need for a mixing system which resists packing and still economically imparts a uniform color to landscaping materials.